1. Field
One or more embodiments of the present invention relate to an additive for an electrolyte of a lithium secondary battery, an organic electrolyte solution including the additive, and a lithium battery including the organic electrolyte solution.
2. Description of the Related Art
Lithium batteries are used as driving (energy) sources of portable electronic devices, such as camcorders, mobile phones, and laptop computers. Lithium secondary batteries are rechargeable at high rates and have a high energy density per unit weight (about three times higher than that of the conventional lead storage batteries, nickel-cadmium (Ni—Cd) batteries, nickel-hydrogen batteries, or nickel-zinc batteries).
A lithium battery operating at a high driving voltage is incompatible with an aqueous electrolyte solution highly reactive to lithium. For this reason, the lithium battery normally uses an organic electrolyte solution. The organic electrolyte solution may be prepared by dissolving a lithium salt in an organic solvent. An appropriate organic solvent may be stable at high voltages, may have a high ionic conductivity, a high dielectric constant, and a low viscosity.
Using a carbonate-based polar or non-aqueous solvent in a lithium battery may cause a side reaction between an anode (and/or a cathode) and an electrolyte solution during initial charging, and consequentially lead to an irreversible reaction using excess charges.
The irreversible reaction may result in a passivation layer such as a solid electrolyte interface (SEI) layer on a surface of the anode. The SEI layer may prevent decomposition of the electrolyte and also serve as an ion channel. The higher the stability of the SEI layer and the lower the resistance of the SEI layer, the longer the the lithium battery life may be.
The irreversible reaction may also form a protection layer on a surface of the cathode. The protection layer may prevent decomposition of the electrolyte solution and also serve as an ion channel. The higher the stability of the protection layer at high temperature, the longer the lithium battery life may be.
A variety of additives are used to stabilize the SEI layer and/or the protective layer. However, when a conventional additive is used, the SEI layer may be prone to deterioration at high temperatures. That is, the SEI layer and/or the protection layer may have poor stability at high temperatures.
Therefore, there is a demand for an organic electrolyte solution for forming an SEI layer and/or protective layer with improved stability at high temperatures.